lt1083/lt1084/lt1085 - 7.5a, 5a, 3a low dropout positive ... · lt1083/lt1084/lt 1085 1 108345 for...

LT1083/LT1084/LT1085

1108345fh

For more information www.linear.com/LT1083

Typical applicaTion

DescripTion

7.5A, 5A, 3A Low DropoutPositive Adjustable Regulators

The LT®1083 series of positive adjustable regulators are designed to provide 7.5A, 5A and 3A with higher efficiency than currently available devices. All internal circuitry is designed to operate down to 1V input-to-output differential and the dropout voltage is fully specified as a function of load current. Dropout is guaranteed at a maximum of 1.5V at maximum output current, decreasing at lower load cur-rents. On-chip trimming adjusts the reference voltage to 1%. Current limit is also trimmed, minimizing the stress on both the regulator and power source circuitry under overload conditions.

The LT1083/LT1084/LT1085 devices are pin compatible with older 3-terminal regulators. A 10µF output capacitor is required on these new devices. However, this is included in most regulator designs.

Unlike PNP regulators, where up to 10% of the output cur-rent is wasted as quiescent current, the LT1083 quiescent current flows into the load, increasing efficiency.

FeaTures

applicaTions

n 3-Terminal Adjustable n Output Current of 3A, 5A or 7.5A n Operates Down to 1V Dropout n Guaranteed Dropout Voltage at Multiple Current Levels n Line Regulation: 0.015% n Load Regulation: 0.1% n 100% Thermal Limit Functional Test n Fixed Versions Available n Available in 3-Lead Plastic TO-220 and DD Packages

n High Efficiency Linear Regulators n Post Regulators for Switching Supplies n Constant Current Regulators n Battery Chargers

DEVICE OUTPUT CURRENT*

LT1083 LT1084 LT1085

7.5A 5.0A 3.0A

*For a 1.5A low dropout regulator see the LT1086 data sheet.

121Ω1%

IN OUT

ADJ

365Ω1%

10µF

5V AT 7.5ALT1083VIN ≥ 6.5V

1083/4/5 ADJ TA01

+10µF*TANTALUM

+

*REQUIRED FOR STABILITY

5V, 7.5A Regulator

OUTPUT CURRENT0

INPU

T/OU

TPUT

VOL

TAGE

DIF

FERE

NTIA

L (V

) 2

1

0

1083/4/5 ADJ TA02

IFULL LOAD

Dropout Voltage vs Output Current

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and UltraFast and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

http://www.linear.com/LT1083


LT1083/LT1084/LT1085

2108345fh


preconDiTioning

absoluTe MaxiMuM raTingsPower Dissipation ............................... Internally LimitedInput-to-Output Voltage Differential

C-Grades ...............................................................30V I-Grades ................................................................30V M-Grades (OBSOLETE) ........................................35V

Operating Junction Temperature Range (Note 9) C-Grades: Control Section ................... 0°C to 125°C Power Transistor ................. 0°C to 150°C I-Grades: Control Section ...............– 40°C to 125°C Power Transistor .............– 40°C to 150°C

M-Grades: (OBSOLETE) Control Section ...............– 55°C to 150°C

Power Transistor ............. –55°C to 200°CStorage Temperature Range ..................–65°C to 150°CLead Temperature (Soldering, 10 sec) ................... 300°C

100% thermal shutdown functional test.

(Note 1)

T PACKAGE3-LEAD PLASTIC TO-220

FRONT VIEW

TABIS

OUTPUT

3

2

1

VIN

VOUT

ADJ

θJA = 50°C/W

VIN

VOUT

ADJ

P PACKAGE3-LEAD PLASTIC TO-3P

FRONT VIEWTAB IS

OUTPUT

3

2

1

θJA = 35°C/W

OBSOLETE PACKAGE

1

2

VIN CASE ISOUTPUT

BOTTOM VIEW

ADJ

K PACKAGE2-LEAD TO-3 METAL CAN

θJA = 35°C/W

OBSOLETE PACKAGE

VIN

VOUT

ADJ

3

2

1

M PACKAGE3-LEAD PLASTIC DD

FRONT VIEW

TABIS

OUTPUT

3

2

1

θJA = 30°C/W*

*WITH PACKAGE SOLDERED TO 0.5IN2 COPPER AREA OVER BACKSIDE GROUND PLANE OR INTERNAL POWER PLANE. θJA CAN VARY

FROM 20°C/W TO >40°C/W DEPENDING ON MOUNTING TECHNIQUE

pin conFiguraTion


LT1083/LT1084/LT1085

3108345fh


orDer inForMaTionLEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

LT1083CP#PBF NA LT1083CP 3-Lead Plastic TO-3P Control: 0°C to 125°C Power: 0°C to 150°C

LT1084CP#PBF NA LT1084CP 3-Lead Plastic TO-3P Control: 0°C to 125°C Power: 0°C to 150°C

OBSOLETE PACKAGE

LT1084CT#PBF NA LT1084CT 3-Lead Plastic TO-220 Control: 0°C to 125°C Power: 0°C to 150°C

LT1084IT#PBF NA LT1084IT 3-Lead Plastic TO-220 Control: –40°C to 125°C Power: –40°C to 150°C

LT1085CT#PBF NA LT1085CT 3-Lead Plastic TO-220 Control: 0°C to 125°C Power: 0°C to 150°C

LT1085IT#PBF NA LT1085IT 3-Lead Plastic TO-220 Control: –40°C to 125°C Power: –40°C to 150°C

LT1085CM#PBF LT1085CM#TRPBF LT1085CM 3-Lead Plastic DD Control: 0°C to 125°C Power: 0°C to 150°C

LT1085IM#PBF LT1085IM#TRPBF LT1085IM 3-Lead Plastic DD Control: –40°C to 125°C Power: –40°C to 150°C

LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

LT1083CP NA LT1083CP 3-Lead Plastic TO-3P Control: 0°C to 125°C Power: 0°C to 150°C

LT1084CP NA LT1084CP 3-Lead Plastic TO-3P Control: 0°C to 125°C Power: 0°C to 150°C

OBSOLETE PACKAGE

LT1084CT NA LT1084CT 3-Lead Plastic TO-220 Control: 0°C to 125°C Power: 0°C to 150°C

LT1084IT NA LT1084IT 3-Lead Plastic TO-220 Control: –40°C to 125°C Power: –40°C to 150°C

LT1085CT NA LT1085CT 3-Lead Plastic TO-220 Control: 0°C to 125°C Power: 0°C to 150°C

LT1085IT NA LT1085IT 3-Lead Plastic TO-220 Control: –40°C to 125°C Power: –40°C to 150°C

LT1085CM LT1085CM#TR LT1085CM 3-Lead Plastic DD Control: 0°C to 125°C Power: 0°C to 150°C

LT1085IM LT1085IM#TR LT1085IM 3-Lead Plastic DD Control: –40°C to 125°C Power: –40°C to 150°C


LT1083/LT1084/LT1085

4108345fh


LEAD BASED FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE

LT1083CK NA LT1083CK 2-Lead TO-3 Metal Can Control: 0°C to 125°C Power: 0°C to 150°C

LT1083MK NA LT1083MK 2-Lead TO-3 Metal Can Control: –55°C to 150°C Power: –55°C to 200°C





OBSOLETE PACKAGE

Consult LTC Marketing for parts specified with wider operating temperature ranges.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/

orDer inForMaTion


LT1083/LT1084/LT1085

5108345fh


elecTrical characTerisTics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.

PARAMETER CONDITIONS MIN TYP MAX UNITS

Reference Voltage IOUT = 10mA, TJ = 25°C, (VIN – VOUT) = 3V 10mA ≤ IOUT ≤ IFULL_LOAD 1.5V ≤ (VIN – VOUT) ≤ 25V (Notes 4, 6, 7)

l

1.238

1.225

1.250

1.250

1.262

1.270

V

V

Line Regulation ILOAD = 10mA, 1.5V ≤ (VIN – VOUT) ≤ 15V, TJ = 25°C (Notes 2, 3)

l

0.015 0.035

0.2 0.2

% %

M-Grade: 15V ≤ (VIN – VOUT) ≤ 35V (Notes 2, 3) l 0.05 0.5 %

C-, I-Grades: 15V ≤ (VIN – VOUT) ≤ 30V (Notes 2, 3) l 0.05 0.5 %

Load Regulation (VIN – VOUT) = 3V, 10mA ≤ IOUT ≤ IFULL_LOAD, TJ = 25°C (Notes 2, 3, 4, 6)

l

0.1 0.2

0.3 0.4

% %

Dropout Voltage ∆VREF = 1%, IOUT = IFULL_LOAD (Notes 5, 6, 8) l 1.3 1.5 V

Current Limit LT1083 LT1084 LT1085

(VIN – VOUT) = 5V (VIN – VOUT) = 25V (VIN – VOUT) = 5V (VIN – VOUT) = 25V (VIN – VOUT) = 5V (VIN – VOUT) = 25V

l

l

l

l

l

l

8.0 0.4 5.5 0.3 3.2 0.2

9.5 1.0 6.5 0.6 4.0 0.5

A A A A A A

Minimum Load Current (VIN – VOUT) = 25V l 5 10 mA

Thermal Regulation LT1083 LT1084 LT1085

TA = 25°C, 30ms Pulse 0.002 0.003 0.004

0.010 0.015 0.020

%/W %/W %/W

Ripple Rejection f = 120Hz, CADJ = 25µF, COUT = 25µF Tantalum IOUT = IFULL_LOAD, (VIN – VOUT) = 3V (Notes 6, 7, 8)

l 60 75 dB

Adjust Pin Current TJ = 25°C

l

55 120

µA µA

Adjust Pin Current Change 10mA ≤ IOUT ≤ IFULL_LOAD, 1.5V ≤ (VIN – VOUT) ≤ 25V (Note 6) l 0.2 5 µA

Temperature Stability l 0.5 %

Long-Term Stability TA = 125°C, 1000 Hrs 0.3 1 %

RMS Output Noise (% of VOUT) TA = 25°C, 10Hz = ≤ f ≤ 10kHz 0.003 %

Thermal Resistance Junction-to-Case LT1083 LT1084 LT1085

Control Circuitry/Power Transistor K Package P Package K Package P Package T Package K Package M, T Package

0.6/1.6 0.5/1.6

0.75/2.3 0.65/2.3 0.65/2.7 0.9/3.0 0.7/3.0

°C/W °C/W °C/W °C/W °C/W °C/W °C/W


LT1083/LT1084/LT1085

6108345fh


elecTrical characTerisTicsNote 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime.Note 2: See thermal regulation specifications for changes in output voltage due to heating effects. Load and line regulation are measured at a constant junction temperature by low duty cycle pulse testing.Note 3: Line and load regulation are guaranteed up to the maximum power dissipation (60W for the LT1083, 45W for the LT1084 (K, P), 30W for the LT1084 (T) and 30W for the LT1085). Power dissipation is determined by the input/output differential and the output current. Guaranteed maximum power dissipation will not be available over the full input/output voltage range.

Note 4: IFULL_LOAD is defined in the current limit curves. The IFULL_LOAD curve is defined as the minimum value of current limit as a function of input-to-output voltage. Note that the 60W power dissipation for the LT1083 (45W for the LT1084 (K, P), 30W for the LT1084 (T), 30W for the LT1085) is only achievable over a limited range of input-to-output voltage.Note 5: Dropout voltage is specified over the full output current range of the device. Test points and limits are shown on the Dropout Voltage curve.Note 6: For LT1083 IFULL_LOAD is 5A for –55°C ≤ TJ < – 40°C and 7.5A for TJ ≥ –40°C.Note 7: 1.7V ≤ (VIN – VOUT) ≤ 25V for LT1084 at –55°C ≤ TJ ≤ – 40°C.Note 8: Dropout is 1.7V maximum for LT1084 at –55°C ≤ TJ ≤ –40°C.Note 9: The LT1083/LT1084/LT1085 regulators are tested and specified under pulse load conditions such that TJ ≅ TA. The C-grade LT1083/LT1084/LT1085 are 100% tested at 25°C.The I-grade LT1084/LT1085 are guaranteed over the full –40°C to 125°C operating ambient temperature range.


LT1083/LT1084/LT1085

7108345fh


Typical perForMance characTerisTics

OUTPUT CURRENT (A)0

MIN

IMUM

INPU

T/OU

TPUT

DIF

FERE

NTIA

L (V

)

1

2

LT1083/4/5 ADJ G01

01 2 3 4 5 6 7 8 9 10

INDICATES GUARANTEED TEST POINT

–40°C ≤ TJ ≤ 150°C

0°C ≤ TJ ≤ 125°C

TJ = 150°C

TJ = 25°C

TJ = –55°C

INPUT/OUTPUT DIFFERENTIAL (V)0

SHOR

T-CI

RCUI

T CU

RREN

T (A

)

8

10

12

15 25

LT1083/4/5 ADJ G02

6

4

5 10 20 30 35

2

0

25°C

150°C

IFULL LOADGUARANTEED

–55°C

TEMPERATURE (°C)–50

–0.20

OUTP

UT V

OLTA

GE D

EVIA

TION

(%)

–0.15

–0.10

–0.05

0

0 50 100 150

LT1083/4/5 ADJ G03

0.05

0.10

–25 25 75 125

∆I = 7.5A

OUTPUT CURRENT (A)0

0

MIN

IMUN

INPU

T/OU

TPUT

DIF

FERE

NTIA

L (V

)

1

1 2 3 4

LT1083/4/5 ADJ G04

5

2

6


–55°C ≤ TJ ≤ 150°C

0°C ≤ TJ ≤ 125°C

TJ = 150°C

TJ = –55°C

TJ = 25°C


0

SHOR

T-CI

RCUI

T CU

RREN

T (A

)

1

3

4

5

10

7

10 20 25

LT1083/4/5 ADJ G05

2

8

9

6

5 15 30 35

25°C–55°C

150°C

GUARANTEEDIFULL LOAD


–0.20

–0.15

–0.10

–0.05

0.05

0.10

OUTP

UT V

OLTA

GE D

EVIA

TION

(%)0

0 50 100 150

LT1083/4/5 ADJ G06

–25 25 75 125

∆I = 5A


–0.20

–0.15

–0.10

–0.05

0.05

0.10

OUTP

UT V

OLTA

GE D

EVIA

TION

(%)

0

0 50 100 150

LT1083/4/5 ADJ G09

–25 25 75 125

∆I = 3A


SHOR

T-CI

RCUI

T CU

RREN

T (A

)

4

5

6

15 25

LT1083/4/5 ADJ G08

3

2

5 10 20 30 35

1

0

25°C

–55°C

IFULL LOADGUARANTEED

150°C

OUTPUT CURRENT (A)0

0

MIN

IMUM

INPU

T/OU

TPUT

DIF

FERE

NTIA

L (V

)

1

2

1 2

LT1083/4/5 ADJ G07

3 4


TJ = 150°CTJ = 25°C

–55°C ≤ TJ ≤ 150°C

TJ = –55°C

0°C ≤ TJ ≤ 125°C

LT1083 Dropout Voltage

LT1083 Short-Circuit Current

LT1083 Load Regulation








LT1083/LT1084/LT1085

8108345fh




0

MIN

IMUM

OPE

RATI

NG C

URRE

NT (m

A)

1

3

4

5

10

7

10 20 25

LT1083/4/5 ADJ G10

2

8

9

6

5 15 30 35

TJ = –55°C

TJ = 150°C

TJ = 25°C


1.27

1.26

1.25

1.24

1.23

REFE

RENC

E VO

LTAG

E (V

)

0 50 100 150

LT1083/4/5 ADJ G11

–25 25 75 125TEMPERATURE (°C)

–50

100

90

80

70

60

50

40

30

20

10

0

ADJU

ST P

IN C

URRE

NT (µ

A)

0 50 100 150

LT1083/4/5 ADJ G12

–25 25 75 125

FREQUENCY (Hz)

RIPP

LE R

EJEC

TION

(dB)

100

90

80

70

60

50

40

30

20

10

010 1k 10k 100k

1083/4/5 ADJ G13

100

VRIPPLE≤ 0.5VP-P

VRIPPLE ≤ 3VP-P

(VIN – VOUT) ≥ 3V

(VIN – VOUT) ≥ VDROPOUT

CADJ = 200µF AT FREQUENCIES < 60HzCADJ = 25µF AT FREQUENCIES > 60HzIOUT = 7A

OUTPUT CURRENT (A)0

RIPP

LE R

EJEC

TION

(dB)

100

90

80

70

60

50

40

30

20

10

02 4 5

1083/4/5 ADJ G14

1 3 6 7 8

VOUT = 5VCADJ = 25µFCOUT = 25µF

fR = 120HzVRIPPLE ≤ 3VP-P

fR = 20kHzVRIPPLE ≤ 0.5VP-P

CASE TEMPERATURE (°C)50

POW

ER (W

)

100

90

80

70

60

50

40

30

20

10

0

LT1083/4/5 ADJ G15

60 70 80 90 100 110 120 130 140 150

LT1083MK

LT1083CP

LT1083CK

* AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE

FREQUENCY (Hz)

RIPP

LE R

EJEC

TION

(dB)

100

90

80

70

60

50

40

30

20

10

010 1k 10k 100k

1083/4/5 ADJ G16

100

VRIPPLE ≤ 0.5VP-PVRIPPLE ≤ 3VP-P




OUTPUT CURRENT (A)0

RIPP

LE R

EJEC

TION

(dB)

100

90

80

70

60

50

40

30

20

10

02 4 5

1083/4/5 ADJ G17

1 3





POW

ER (W

)

60

50

40

30

20

10

0

LT1083/4/5 ADJ G18

60 70 80 90 100 110 120 130 140 150

LT1084MK

LT1084CTLT1084CP


LT1084CK

Minimum Operating Current Temperature Stability Adjust Pin Current

LT1083 Ripple Rejection

LT1083 Ripple Rejection vs Current

LT1083 Maximum Power Dissipation*





LT1083/LT1084/LT1085

9108345fh



TIME (µs)0

OUTP

UT V

OLTA

GEDE

VIAT

ION

(V)

LOAD

CUR

RENT

(A)

0.3

0.2

0.1

0

–0.1

–0.2

–0.3

3

2

1

050

1083/4/5 ADJ G24

100

CADJ = 0

CADJ = 1µF

CIN = 1µFCOUT = 10µF TANTALUM

VOUT=10VVIN=13VPRELOAD=100mA

FREQUENCY (Hz)

RIPP

LE R

EJEC

TION

(dB)

100

90

80

70

60

50

40

30

20

10

010 1k 10k 100k

1083/4/5 ADJ G19

100

VRIPPLE≤ 0.5VP-P

VRIPPLE ≤ 3VP-P




OUTPUT CURRENT (A)0

RIPP

LE R

EJEC

TION

(dB)

100

90

80

70

60

50

40

30

20

10

01.0 1.5 2.5 3.0

1083/4/5 ADJ G20

0.5 2.0





POW

ER (W

)

50

40

30

20

10

0

LT1083/4/5 ADJ G21

60 70 80 90 100 110 120 130 140 150

LT1085MK

LT1085CT

LT1085CK


TIME (µs)0

OUTP

UT V

OLTA

GEDE

VIAT

ION

(V)

LOAD

CUR

RENT

(A)

0.6

0.4

0.2

0

–0.2

–0.4

8

6

4

2

050

1083/4/5 ADJ G22

100

CADJ = 0 CADJ = 1µF



TIME (µs)0

OUTP

UT V

OLTA

GEDE

VIAT

ION

(V)

LOAD

CUR

RENT

(A)

0.6

0.4

0.2

0

–0.2

–0.4

–0.6

6

4

2

050

1083/4/5 ADJ G23

100

CADJ = 0

CADJ = 1µF



TIME (µs)0

OUTP

UT V

OLTA

GEDE

VIAT

ION

(mV)

INPU

TDE

VIAT

ION

(V)

60

40

20

0

–20

–40

–60

14

13

12

100

1083/4/5 ADJ G26

200

CADJ = 0CADJ = 1µF

VOUT = 10VIIN = 0.2ACIN = 1µF TANTALUMCOUT = 10µF TANTALUM

TIME (µs)0

OUTP

UT V

OLTA

GEDE

VIAT

ION

(mV)

INPU

TDE

VIAT

ION

(V)

60

40

20

0

–20

–40

–60

14

13

12

100

1083/4/5 ADJ G27

200

CADJ = 0CADJ = 1µF


TIME (µs)0

OUTP

UT V

OLTA

GEDE

VIAT

ION

(mV)

INPU

TDE

VIAT

ION

(V)

150

100

50

0

–50

–100

–150

14

13

12

100

1083/4/5 ADJ G25

200

CADJ = 0

CADJ = 1µF





LT1083 Load Transient Response



LT1083 Line Transient Response




LT1083/LT1084/LT1085

10108345fh


applicaTions inForMaTionThe LT1083 family of 3-terminal adjustable regulators is easy to use and has all the protection features that are expected in high performance voltage regulators. They are short-circuit protected, and have safe area protection as well as thermal shutdown to turn off the regulator should the junction temperature exceed about 165°C.

These regulators are pin compatible with older 3-terminal adjustable devices, offer lower dropout voltage and more precise reference tolerance. Further, the reference stability with temperature is improved over older types of regula-tors. The only circuit difference between using the LT1083 family and older regulators is that this new family requires an output capacitor for stability.

Stability

The circuit design used in the LT1083 family requires the use of an output capacitor as part of the device frequency compensation. For all operating conditions, the addition of a 150µF aluminium electrolytic or a 22µF solid tantalum

on the output will ensure stability. Normally, capacitors much smaller than this can be used with the LT1083. Many different types of capacitors with widely varying charac-teristics are available. These capacitors differ in capacitor tolerance (sometimes ranging up to ±100%), equivalent series resistance, and capacitance temperature coefficient. The 150µF or 22µF values given will ensure stability.

When the adjustment terminal is bypassed to improve the ripple rejection, the requirement for an output capacitor increases. The value of 22µF tantalum or 150µF aluminum covers all cases of bypassing the adjustment terminal. Without bypassing the adjustment terminal, smaller capacitors can be used with equally good results and the table below shows approximately what size capacitors are needed to ensure stability.

Recommended Capacitor ValuesINPUT OUTPUT ADJUSTMENT

10µF 10µF

10µF Tantalum, 50µF Aluminum 22µF Tantalum, 150µF Aluminum

None 20µF

block DiagraM

–

+

THERMALLIMIT

VADJ

VOUT

1083/4/5 ADJ BD

VIN


LT1083/LT1084/LT1085

11108345fh


applicaTions inForMaTion

R1

R2

IN OUT

ADJ

VOUTLT1083

D11N4002

(OPTIONAL)

VIN

1083/4/5 ADJ F00

COUT150µF

+

CADJ10µF

+

Normally, capacitor values on the order of 100µF are used in the output of many regulators to ensure good transient response with heavy load current changes. Output capaci-tance can be increased without limit and larger values of output capacitor further improve stability and transient response of the LT1083 regulators.

Another possible stability problem that can occur in mono-lithic IC regulators is current limit oscillations. These can occur because, in current limit, the safe area protection exhibits a negative impedance. The safe area protection decreases the current limit as the input-to-output volt-age increases. That is the equivalent of having a negative resistance since increasing voltage causes current to decrease. Negative resistance during current limit is not unique to the LT1083 series and has been present on all power IC regulators. The value of the negative resistance is a function of how fast the current limit is folded back as input-to-output voltage increases. This negative resis-tance can react with capacitors or inductors on the input to cause oscillation during current limiting. Depending on the value of series resistance, the overall circuitry may end up unstable. Since this is a system problem, it is not necessarily easy to solve; however, it does not cause any problems with the IC regulator and can usually be ignored.

Protection Diodes

In normal operation, the LT1083 family does not need any protection diodes. Older adjustable regulators re-quired protection diodes between the adjustment pin and the output and from the output to the input to prevent overstressing the die. The internal current paths on the LT1083 adjustment pin are limited by internal resistors. Therefore, even with capacitors on the adjustment pin, no protection diode is needed to ensure device safety under short-circuit conditions.

Diodes between input and output are usually not needed. The internal diode between the input and the output pins of the LT1083 family can handle microsecond surge cur-rents of 50A to 100A. Even with large output capacitances, it is very difficult to get those values of surge currents in normal operations. Only with a high value of output capacitors, such as 1000µF to 5000µF and with the input

pin instantaneously shorted to ground, can damage occur. A crowbar circuit at the input of the LT1083 can generate those kinds of currents, and a diode from output to input is then recommended. Normal power supply cycling or even plugging and unplugging in the system will not generate current large enough to do any damage.

The adjustment pin can be driven on a transient basis ±25V, with respect to the output without any device deg-radation. Of course, as with any IC regulator, exceeding the maximum input to output voltage differential causes the internal transistors to break down and none of the protection circuitry is functional.

Overload Recovery

Like any of the IC power regulators, the LT1083 has safe area protection. The safe area protection decreases the current limit as input-to-output voltage increases and keeps the power transistor inside a safe operating region for all values of input-to-output voltage. The LT1083 protection is designed to provide some output current at all values of input-to-output voltage up to the device breakdown.

When power is first turned on, as the input voltage rises, the output follows the input, allowing the regulator to start up into very heavy loads. During the start-up, as the input voltage is rising, the input-to-output voltage differential remains small, allowing the regulator to supply large output currents. With high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to recover. Older regulators, such as the 7800 series, also exhibited this phenomenon, so it is not unique to the LT1083.


LT1083/LT1084/LT1085

12108345fh


applicaTions inForMaTion

Figure 1. Basic Adjustable Regulator

R1

R2

IN OUT

IADJ50µA

ADJ

VOUTLT1083VIN

1083/4/5 ADJ F01

VREF

VOUT = VREF 1 + + IADJ R2 R2R1( )

Figure 2. Connections for Best Load Regulation

LT1083 OUTINVIN

ADJ

RPPARASITIC

LINE RESISTANCE

R1*

*CONNECT R1 TO CASE CONNECT R2 TO LOAD

1083/4/5 ADJ F02

RL

R2*

The problem occurs with a heavy output load when the input voltage is high and the output voltage is low, such as immediately after removal of a short. The load line for such a load may intersect the output current curve at two points. If this happens, there are two stable output operat-ing points for the regulator. With this double intersection, the power supply may need to be cycled down to zero and brought up again to make the output recover.

Ripple Rejection

The typical curves for ripple rejection reflect values for a bypassed adjustment pin. This curve will be true for all values of output voltage. For proper bypassing and ripple rejection approaching the values shown, the impedance of the adjust pin capacitor at the ripple frequency should be less than the value of R1, (normally 100Ω to 120Ω). The size of the required adjust pin capacitor is a function of the input ripple frequency. At 120Hz the adjust pin capacitor should be 25µF if R1 = 100Ω. At 10kHz only 0.22µF is needed.

For circuits without an adjust pin bypass capacitor, the ripple rejection will be a function of output voltage. The output ripple will increase directly as a ratio of the output voltage to the reference voltage (VOUT/VREF). For example, with the output voltage equal to 5V and no adjust pin capaci-tor, the output ripple will be higher by the ratio of 5V/1.25V or four times larger. Ripple rejection will be degraded by 12dB from the value shown on the typical curve.

Output Voltage

The LT1083 develops a 1.25V reference voltage between the output and the adjust terminal (see Figure 1). By placing a resistor R1 between these two terminals, a constant current is caused to flow through R1 and down through R2 to set the overall output voltage. Normally this current is the specified minimum load current of 10mA. Because IADJ is very small and constant when compared with the current through R1, it represents a small error and can usually be ignored.

Load Regulation

Because the LT1083 is a 3-terminal device, it is not pos-sible to provide true remote load sensing. Load regulation will be limited by the resistance of the wire connecting the regulator to the load. The data sheet specification for load regulation is measured at the bottom of the package. Negative side sensing is a true Kelvin connection, with the bottom of the output divider returned to the negative side of the load. Although it may not be immediately obvious, best load regulation is obtained when the top of the resis-tor divider R1 is connected directly to the case not to the load. This is illustrated in Figure 2. If R1 were connected to the load, the effective resistance between the regulator and the load would be:

RP • R2+R1

R1⎛

⎝⎜

⎞

⎠⎟,RP = Parasitic Line Resistance


LT1083/LT1084/LT1085

13108345fh


applicaTions inForMaTionConnected as shown, RP is not multiplied by the divider ratio. RP is about 0.004Ω per foot using 16-gauge wire. This translates to 4mV/ft at 1A load current, so it is important to keep the positive lead between regulator and load as short as possible and use large wire or PC board traces.

Thermal Considerations

The LT1083 series of regulators have internal power and thermal limiting circuitry designed to protect the device under overload conditions. For continuous normal load conditions however, maximum junction temperature rat-ings must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. This includes junction-to-case, case- to-heat sink interface, and heat sink resistance itself. New thermal resistance specifications have been developed to more accurately reflect device temperature and ensure safe operating temperatures. The data section for these new regulators provides a separate thermal resistance and maximum junction temperature for both the Control Section and the Power Transistor. Previous regulators, with a single junction-to-case thermal resistance specification, used an average of the two values provided here and therefore could allow excessive junction temperatures under certain conditions of ambient temperature and heat sink resistance. To avoid this possibility, calculations should be made for both sections to ensure that both thermal limits are met.

Junction-to-case thermal resistance is specified from the IC junction to the bottom of the case directly below the die. This is the lowest resistance path for heat flow. Proper mounting is required to ensure the best possible thermal flow from this area of the package to the heat sink. Thermal

compound at the case-to-heat sink interface is strongly recommended. If the case of the device must be electri-cally isolated, a thermally conductive spacer can be used, as long as its added contribution to thermal resistance is considered. Note that the case of all devices in this series is electrically connected to the output.

For example, using an LT1083CK (TO-3, Commercial) and assuming:

VIN (Max Continuous) = 9V, VOUT = 5V, IOUT = 6A,

TA = 75°C, θHEAT SINK = 1°C/W,

θCASE-TO-HEAT SINK = 0.2°C/W for K package with thermal compound.

Power dissipation under these conditions is equal to:

PD = (VIN – VOUT )(IOUT) = 24W

Junction temperature will be equal to:

TJ = TA + PD (θHEAT SINK + θCASE-TO-HEAT SINK + θJC)

For the Control Section:

TJ = 75°C + 24W (1°C/W + 0.2°C/W + 0.6°C/W) = 118°C 118°C < 125°C = TJMAX (Control Section Commercial Range)

For the Power Transistor:

TJ = 75°C + 24W (1°C/W + 0.2°C/W + 1.6°C/W) = 142°C 142°C < 150°C = TJMAX (Power Transistor Commercial Range)

In both cases the junction temperature is below the maxi-mum rating for the respective sections, ensuring reliable operation.


LT1083/LT1084/LT1085

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Typical applicaTion7.5A Variable Regulator

15V

15V

15V

110VAC

T1TRIADF-269U

–

+

–

+

++

–

+

OUTIN LT1083 OUTIN

ADJ

C30B

C30B

3

20Ω

20Ω

1 2

L1mH

T2

1N4003

1N4148

1N4003

1N914

C150,000µF

100µF

LT1004-1.2

1N4003

1µF

0.1µF

1µF

100pF

560Ω16k*

16k*

LT1004-1.2

11k*

11k*

0V TO 35VOA TO 7.5A

10k

82k 15k

2

2

2

3

3

3

8

8

–15V

–15V

–15V15V

4

4

4

7

7

1

1

200k

750Ω*

2kOUTPUTADJUST

2.7k

–15V

1.5k

15K

10k

2N3904

NC

86

7

1

LT1011

LT1011

LM301A* 1% FILM RESISTOR

L: DALE TO-5 TYPET2: STANCOR 11Z-2003

GENERAL PURPOSE REGULATOR WITH SCR PREREGULATORTO LOWER POWER DISSIPATION. ABOUT 1.7V DIFFERENTIALIS MAINTAINED ACROSS THE LT1083 INDEPENDENT OF OUTPUTVOLTAGE AND LOAD CURRENT LT1083/4/5 ADJ TA05


LT1083/LT1084/LT1085

15108345fh


Typical applicaTion

LT1083 OUTINVIN

ADJ

LT1083

0.015Ω

OUT

2 FEET #18 WIRE*

IN

ADJ

R1120Ω

R2

*THE #18 WIRE ACTS AS BALLAST RESISTANCE INSURING CURRENT SHARING BETWEEN BOTH DEVICES

LT1083/4/5 ADJ TA03

VOUT = 1.25V 1 +

IOUT = 0A TO 15A

R2R1( )

Paralleling Regulators

Remote Sensing

R1121Ω1%

IN OUT

ADJ

R2365Ω1%

10µF

VOUT5V

LT1083VIN

1083/4/5 ADJ TA04

+

C125µF*

150µF+

+

*C1 IMPROVES RIPPLE REJECTION. XC SHOULD BE < R1 AT RIPPLE FREQUENCY

Improving Ripple Rejection

–

+

LT1083 OUTINVIN

VIN

RETURN

ADJ

RP(MAX DROP 300mV)

121Ω

365Ω

25Ω

10µF

5µF

100µF

1083/4/5 ADJ TA07

RL

VOUT5V

RETURN25Ω

2

6

7

18

100pF

3

4

+

1kLM301A

+

+


LT1083/LT1084/LT1085

16108345fh


Typical applicaTion

High Efficiency Regulator with Switching Preregulator

–

+

VIN28V

28V

470Ω240Ω

2k

28V

4N28

1N914

1N914

LT1011

10k

10k

10k

1k1M

MR1122

1mH

10,000µF

VOUTLT1083 OUTIN

ADJ

1083/4/5 ADJ TA06

+

1.2V to 15V Adjustable Regulator

5V Regulator with Shutdown*

INVIN OUT

TTL

ADJ

1k

1k

10µF100µF

VOUT5V

LT1083

2N3904

1083/4/5 ADJ TA09

+121Ω1%

365Ω1%

*OUTPUT SHUTS DOWN TO 1.3V

+

IN OUT

ADJ

R21k

C1*10µF

VOUT†VIN LT1083

1083/4/5 ADJ TA08

+C2100µF

+R190.9Ω

*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS†VOUT = 1.25V 1 + R2

R1( )


LT1083/LT1084/LT1085

17108345fh


package DescripTion

K2 (TO-3) 0801

.038 – .043(0.965 – 1.09)

.060 – .135(1.524 – 3.429)

.320 – .350(8.13 – 8.89)

.420 – .480(10.67 – 12.19)

.760 – .775(19.30 – 19.69)

.490 – .510(12.45 – 12.95)

R

.167 – .177(4.24 – 4.49)

R

.151 – .161(3.86 – 4.09)DIA, 2PLCS

1.177 – 1.197(29.90 – 30.40)

.655 – .675(16.64 – 17.15)

.067 – .077(1.70 – 1.96)

.210 – .220(5.33 – 5.59)

.425 – .435(10.80 – 11.05)

K Package2-Lead TO-3 Metal Can

(Reference LTC DWG # 05-08-1310)

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

OBSOLETE PACKAGE


http://www.linear.com/designtools/packaging/

LT1083/LT1084/LT1085

18108345fh


M Package3-Lead Plastic DD Pak

(Reference LTC DWG # 05-08-1460 Rev F)

package DescripTionPlease refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

.050 (1.270)

.143 +.012–.020

( )3.632+0.305–0.508

.100(2.54)BSC

.013 – .023(0.330 – 0.584)

.095 – .115(2.413 – 2.921)

.004 +.008–.004

( )0.102+0.203–0.102

.050 ±.012(1.270 ±0.305)

.059(1.499)

.045 – .055(1.143 – 1.397)

.165 – .180(4.191 – 4.572)

.330 – .370(8.382 – 9.398)

.060(1.524)

TYP.390 – .415

(9.906 – 10.541)

15°

.300(7.620)

.075(1.905)

.183(4.648)

.060(1.524)

.060(1.524)

.256(6.502)

BOTTOM VIEW OF DD PAKHATCHED AREA IS SOLDER PLATED

COPPER HEAT SINK

M (DD3) 0212 REV F

.420

.350

.585

.090

.070.100

.420

.276

.325.205

.080

.585

.090

.070.100

RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS

RECOMMENDED SOLDER PAD LAYOUT

NOTE:1. DIMENSIONS IN INCH/(MILLIMETER)2. DRAWING NOT TO SCALE

.320

M Package3-Lead Plastic DD Pak

(Reference LTC DWG # 05-08-1460 Rev F)

DETAIL A

DETAIL A

0° – 7° TYP0° – 7° TYP



LT1083/LT1084/LT1085

19108345fh


OBSOLETE PACKAGE

package DescripTion

P Package3-Lead Plastic TO-3P (Similar to TO-247)

(Reference LTC DWG # 05-08-1450 Rev A)

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

.170 (4.32)MAX

.170 – .215(4.32 – 5.46)

MOUNTING HOLE.115 – .145

(2.92 – 3.68)DIA

.580 – .600(14.73 – 15.24)

.780 – .800(19.81 – 20.32)

.620 – .640(15.75 – 16.26)

.215 (5.46)BSC

.113 – .123(2.87 – 3.12)

.042 – .052(1.07 – 1.32)

.074 – .084(1.88 – 2.13)

.187 – .207(4.75 – 5.26)

.060 – .081(1.52 – 2.06)18° – 22°

3° – 7°

.087 – .102(2.21 – 2.59)

.020 – .040(0.51 – 1.02)

EJECTOR PIN MARKS.105 – .125

(2.67 – 3.18)DIA

P3 0512 REV A

P Package3-Lead Plastic TO-3P (Similar to TO-247))

(Reference LTC DWG # 05-08-1450 Rev A)

.560 – .620(14.22 – 15.75)

.515 – .580(13.08 – 14.73)

.305 – .370(7.75 – 9.40)

.635 – .720(16.13 – 18.29)

.104 – .145(2.64 – 3.68)

.819 – .870(20.80 – 22.10)

BOTTOM VIEW OF TO-3PHATCHED AREA IS SOLDER PLATED

COPPER HEAT SINK

.265 – .293(6.73 – 7.44)

NOTE:1. DIMENSIONS IN INCH/(MILLIMETER)2. DRAWING NOT TO SCALE3. DIMENSIONS ARE INCLUSIVE OF PLATING4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR5. MOLD FLASH SHALL NOT EXCEED .030" (.762mm)



LT1083/LT1084/LT1085

20108345fh


T Package3-Lead Plastic TO-220


package DescripTionPlease refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

.100(2.540)

BSC .028 – .038(0.711 – 0.965)

T3 (TO-220) 0801

.045 – .055(1.143 – 1.397)

.165 – .180(4.191 – 4.572)

.095 – .115(2.413 – 2.921)

.013 – .023(0.330 – 0.584)

.520 – .570(13.208 – 14.478)

.980 – 1.070(24.892 – 27.178)

.218 – .252(5.537 – 6.401)

.050(1.270)

TYP

.147 – .155(3.734 – 3.937)

DIA

.390 – .415(9.906 – 10.541)

.330 – .370(8.382 – 9.398)

.460 – .500(11.684 – 12.700)

.570 – .620(14.478 – 15.748)

.230 – .270(5.842 – 6.858)

T Package3-Lead Plastic TO-220




LT1083/LT1084/LT1085

21108345fh


Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

revision hisToryREV DATE DESCRIPTION PAGE NUMBER

H 06/15 Obsolete TO-3P package. 2, 19

(Revision history begins at Rev H)


LT1083/LT1084/LT1085

22108345fh

For more information www.linear.com/LT1083 LINEAR TECHNOLOGY CORPORATION 1994

LT 0615 REV H • PRINTED IN USALinear Technology Corporation1630 McCarthy Blvd., Milpitas, CA 95035-7417(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LT1083

relaTeD parTs

Typical applicaTionsAutomatic Light Control Protected High Current Lamp Driver

INVIN OUT

ADJ

10µF 100µF

LT1083

1083/4/5 ADJ TA10

1.2k+

OUT

TTL ORCMOS

IN

ADJ

15V

12V5A

LT1083

1083/4/5 ADJ TA11

10k

PART NUMBER DESCRIPTION COMMENTS

LT1129 700mA Micropower Low Dropout Regulator 50µA Quiescent Current

LT1175 500mA Negative Low Dropout Micropower Regulator 45µA IQ, 0.26V Dropout Voltage, SOT-223 Package

LT1185 3A Negative Low Dropout Regulator VIN: –4.5V to –35V, 0.8V Dropout Voltage, DD-Pak and TO-220 Packages

LT1529 3A Low Dropout Regulator with 50µA IQ 500mV Dropout Voltage

LT1580 7A, Very Low Dropout Regulator 0.54V Dropout at 7A, Fixed 2.5VOUT and Adjustable

LT1581 10A, Very Low Dropout Regulator 0.63V Dropout at 10A, Fixed 2.5VOUT and Adjustable

LT1584/LT1585/LT1587

7A/4.6A/3A Fast Response LDOs Fast Transient Response for Microprocessor Applications

LT1761 Series 100mA, Low Noise, Low Dropout Micropower Regulators in SOT-23

20µA Quiescent Current, 20µVRMS Noise, SOT-23 Package

LT1762 Series 150mA, Low Noise, LDO Micropower Regulators 25µA Quiescent Current, 20µVRMS Noise, MSOP Package

LT1763 Series 500mA, Low Noise LDO Micropower Regulators 30µA Quiescent Current, 20µVRMS Noise, SO-8 Package

LT1764 3A Low Noise Fast Transient Response LDO 40µVRMS Noise, 5-Lead DD Package

LT1962 300mA, Low Noise LDO Micropower Regulator 20µVRMS Noise, MSOP Package

LT1963 1.5A, Low Noise, Fast Transient Response LDO 40µVRMS Noise, SOT-223 Package

LT1964 200mA, Low Noise, Negative LDO 340mV Dropout Voltage, Low Noise 30µVRMS, VIN = –1.8V to –20V, ThinSOT™ and 3mm × 3mm DFN-8 Packages

LT3015 1.5A, Low Noise, Negative Linear Regulator with Precision Current Limit

VIN: –1.8V to –30V, VOUT: –1.22V to –29.5V, Dropout Voltage: 310mV, Precision Current Limit with Foldback, Low Output Noise: 60μVRMS (10Hz to 100kHz), TO-220, DD-Pak, DFN and MSOP Packages

LT3080/ LT3080-1

1.1A, Parallelable, Low Noise, Low Dropout Linear Regulator 300mV Dropout Voltage (2-Supply Operation), Low Noise: 40µVRMS, VIN: 1.2V to 36V, VOUT: 0V to 35.7V, Stable with Ceramic Caps, TO-220, DD-Pak, SOT-223, MS8E and 3mm × 3mm DFN-8 Packages; "-1" Version Has Integrated Internal Ballast Resistor

LT3090 600mA Low Noise Negative LDO with Programmable ILIMIT 300mV Dropout Voltage, 18µVRMS Output Voltage Noise, Parallelable 50μA SET Pin Current: ±1% Initial Accuracy, Positive/Negative Current Monitors Wide Input Voltage Range: –1.5V to –36V, Rail-to-Rail Output Voltage Range: 0V to –32V





















http://www.linear.com/LT3080-1


lt1083/lt1084/lt1085 - 7.5a, 5a, 3a low dropout positive ... · lt1083/lt1084/lt 1085 1 108345 for...

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